Patterning of a magnetoresistance structure including two hard masks

ABSTRACT

A method includes depositing on a substrate a magnetoresistance stack, depositing a first hard mask on the magnetoresistance stack, depositing a first photoresist on the first hard mask, patterning the first photoresist to expose portions of the first hard mask, and etching the exposed portions of the first hard mask to expose a portion of the magnetoresistance stack. The method further includes stripping the first photoresist, etching the exposed portions of the magnetoresistance stack and the first hard mask to form a first intermediate structure having a base and a pillar structure, depositing an etch barrier on the first intermediate structure, and depositing a second hard mask on the etch barrier. A second photoresist is deposited on the second hard mask. The method further includes patterning the second photoresist to expose portions of the second hard mask, etching the exposed portions of the second hard mask, stripping the second photoresist, etching a portion of the second hard mask, a portion of the etch barrier and the base to form a second intermediate structure, and depositing a capping barrier on the second intermediate structure.

BACKGROUND

A magnetic field sensing element is used to describe a variety ofelectronic elements that can sense a magnetic field. The magnetic fieldsensing element can be, but is not limited to, a Hall effect element, amagnetoresistance element, or a magnetotransistor. As is known, thereare different types of Hall effect elements, for example, a planar Hallelement, a vertical Hall element, and a Circular Vertical Hall (CVH)element. There are different types of magnetoresistance elements, forexample, a semiconductor magnetoresistance element such as IndiumAntimonide (InSb), a giant magnetoresistance (GMR) element, for example,a spin valve, an anisotropic magnetoresistance element (AMR), atunneling magnetoresistance (TMR) element, and a magnetic tunneljunction (MTJ). The magnetic field sensing element may be a singleelement or, alternatively, may include two or more magnetic fieldsensing elements arranged in various configurations, e.g., a half bridgeor full (Wheatstone) bridge. Depending on the device type and otherapplication requirements, the magnetic field sensing element may be adevice made of a type IV semiconductor material such as Silicon (Si) orGermanium (Ge), or a type III-V semiconductor material likeGallium-Arsenide (GaAs) or an Indium compound, e.g., Indium-Antimonide(InSb).

SUMMARY

A method includes depositing on a substrate a magnetoresistance stackcomprising a plurality of layers comprising a first set of one or moremagnetoresistance layers and a second set of one or moremagnetoresistance layers, depositing a first hard mask on themagnetoresistance stack, depositing a first photoresist on the firsthard mask, patterning the first photoresist using photolithography toexpose portions of the first hard mask, and etching the exposed portionsof the first hard mask to expose a portion of the magnetoresistancestack. The method further includes stripping the first photoresist,etching the exposed portions of the magnetoresistance stack and thefirst hard mask to form a first intermediate structure having a base anda pillar structure, depositing an etch barrier on the first intermediatestructure, and depositing a second hard mask on the etch barrier. Asecond photoresist is deposited on the second hard mask. The methodfurther includes patterning the second photoresist usingphotolithography to expose portions of the second hard mask, etching theexposed portions of the second hard mask, stripping the secondphotoresist, etching a portion of the second hard mask, a portion of theetch barrier and the base to form a second intermediate structure, anddepositing a capping barrier on the second intermediate structure.

Features may include one or more of the following individually or incombination. The etching of the exposed portions of themagnetoresistance stack and the first hard mask to form the firstintermediate structure having the base and the pillar structure maycomprise etching the exposed portions of the magnetoresistance stack toform the first intermediate structure having the base, the basecomprising a conductive layer on the substrate and an active element onthe conductive layer. Etching the exposed portions of themagnetoresistance stack and the first hard mask to form the firstintermediate structure having the base and the pillar structure maycomprise etching the exposed portions of the magnetoresistance stack andthe first hard mask to form the first intermediate structure having thepillar structure, the pillar structure comprising the first hard mask,capping material, an active element, and a tunneling barrier. Depositingon the substrate the magnetoresistance stack may comprise depositing oneof a tunneling magnetoresistance (TMR) stack or a magnetic tunneljunction (MTJ) stack. Depositing the capping barrier may comprisedepositing a capping barrier comprising silicon nitride. Depositing themagnetoresistance stack on the substrate may comprise depositing amagnetoresistance stack comprising a layer of magnesium oxide.Depositing the magnetoresistance stack on the substrate may comprisedepositing a magnetoresistance stack comprising a layer of siliconnitride. Depositing the magnetoresistance stack on the substrate maycomprise depositing the magnetoresistance stack on the substrate, thesubstrate comprising one of silicon dioxide or silicon nitride.Depositing the first hard mask or the second hard mask may comprisedepositing silicon dioxide. Depositing an etch barrier comprisesdepositing an etch barrier comprising silicon nitride. Etching theexposed portions of the magnetoresistance stack may comprise etchingusing an ion beam etching process. Etching the portion of the secondhard mask, the portion of the etch barrier and the portion of the basemay comprise etching using an ion beam etching process. Depositing onthe substrate a magnetoresistance stack having a plurality of layerscomprising the first set of one or more magnetoresistance layers and thesecond set of one or more magnetoresistance layers may comprisedepositing on the substrate a magnetoresistance stack having theplurality of layers comprising a first set of one or moremagnetoresistance layers comprising one or more active elements and atunneling barrier layer and a second set of one or moremagnetoresistance layers comprising an active element.

Also described is a magnetoresistance structure comprising a basecomprising a conductive layer on the substrate and an active element onthe conductive layer, a pillar structure connected to the base, thepillar structure comprising a first hard mask, a capping material, anactive element, and a tunnel layer, an etching barrier deposited on thepillar and the base, a second hard mask deposited on the etchingbarrier, and a capping barrier deposited on the second hard mask andcovering side walls of the base.

Features may include one or more of the following individually or incombination. The base and the pillar structure may form one of atunneling magnetoresistance (TMR) stack or a magnetic tunnel junction(MTJ) stack. The capping barrier may comprise silicon nitride. Thetunnel layer may comprise a layer of magnesium oxide. The cappingmaterial may comprise a layer of silicon nitride. The magnetoresistancestructure may further comprise a substrate connected to the conductivelayer of the base, wherein the substrate comprises one of silicondioxide or silicon nitride. The first or second hard mask may comprisesilicon dioxide.

DESCRIPTION OF THE DRAWINGS

The foregoing features may be more fully understood from the followingdescription of the drawings. The drawings aid in explaining andunderstanding the disclosed technology. Since it is often impractical orimpossible to illustrate and describe every possible embodiment, theprovided figures depict one or more illustrative embodiments.Accordingly, the figures are not intended to limit the scope of thebroad concepts, systems and techniques described herein. Like numbers inthe figures denote like elements.

FIGS. 1A to 1L are diagrams of one example to pattern amagnetoresistance stack that includes two hard masks; and

FIG. 2 is a flowchart of an example of a process to pattern themagnetoresistance stack that includes two hard masks.

DETAIL DESCRIPTION

Described herein are techniques to pattern a magnetoresistance structurethat includes two hard masks. In particular, the techniques describedherein are used to form bottom contacts for a magnetoresistancestructures such as for example, a GMR, a TMR (such as an MTJ forexample) or hybrid of a GMR and a TMR. In one example, the techniquesdescribed herein improve flatness of an interface between a bottominterconnect and a TMR stack, which in turn improves a magnetic responseof MR sensor element.

Referring to FIG. 1A, a multi-layer magnetoresistance stack is depositedon a substrate, and a hard mask is deposited on the magnetoresistancestack. For example, a magnetoresistance stack 100 that includes layers,102, 103, 104, 105 is deposited on a substrate 101, an etch stop 106 isdeposited on the layers 102-105, and a hard mask 107 is deposited on theetch stop layer. In one example, the magnetoresistance stack 100 may beused in a magnetic field sensing element. In one example, themagnetoresistance stack 100 is a tunneling magnetoresistance (TMR)stack, such as a magnetic tunnel junction (MTJ) stack for example.

In some embodiments, the substrate 101 does not have to supportelectronic circuitry, but may be, for example, a dummy substrate thatonly supports a magnetoresistance element. In one example, the substrate101 may include any material suitable for supporting electroniccircuitry. In some embodiments, the substrate 101 may include asemiconductor material, including but not limited to silicon, germanium,gallium arsenide, and/or other types of semiconductor materials. Inother embodiments, the substrate 101 may include diamond, glass,ceramic, polymer and/or other materials. In one particular example, thesubstrate 101 is silicon dioxide or silicon nitride. In other examples,the substrate 101 may include both semiconductor and non-semiconductormaterials.

In one example, the layer 102 is a bottom contact material that includesa conductor material (e.g., titanium nitride).

In one example, one or more of the layers 103, 104, 105, 106 may includetwo or more sublayers. In one example, the layers 103, 104, 105 mayinclude active elements. In some examples, the layer 104 is a tunnelingbarrier, and in one particular example, the tunneling barrier includesmagnesium oxide or aluminum oxide.

In some examples, the layer 106 is a capping material that includes, forexample, silicon nitride or silicon dioxide. In one example, the hardmask 107 includes silicon dioxide or silicon nitride.

Referring to FIG. 1B, photoresist is deposited on a hard mask andphotolithography is used to pattern the photoresist. For example, aphotoresist 108 is deposited on the hard mask 107 and photolithographyis used to pattern the photoresist 108 to expose portions of the hardmask 106.

Referring to FIGS. 1C and 1D, an etching process is used to etch theexposed portions of the hard mask, and the photoresist is removed. Forexample, an etching process (e.g., reactive ion etching) is used to etchthe hard mask 107 with the photoresist 108 acting as a mask, and afterthe etching of the hard mask 107, the photoresist 108 is stripped away.

Referring to FIG. 1E, the magnetoresistance stack and the hard mask areetched. For example, the exposed portions of the magnetoresistance stack100 and the hard mask 107 are etched using an ion beam etching process.In one particular example, not all of the layers 102, 103, 104, 105 and106 of the magnetoresistance stack 100 are etched. For example, thelayers 102, 103 are not etched, but the layers 104, 105, 106 are etchedto form an intermediate structure 114 with the hard mask 107. Forexample, the remaining portions of layers 103, 104, 105, 106, 107 form apillar structure 110 of the intermediate structure 114 and the layers102, 103 form a base 112 of the intermediate structure 114. In oneparticular example, the tools used during ion beam etching determinesthat the layer 103 is an etch stop barrier and therefore should not beetched.

Referring to FIG. 1F, an etch barrier is deposited on the intermediatestructure 114. For example, an etch barrier 116 is deposited on theremaining magnetoresistance stack completely covering the sides of thepillar structure 110 and is deposited on the base 112. The etch barrier116 includes nonconductive material. In some examples, the etch barrier116 includes silicon nitride or silicon dioxide. The etch barrier 116includes nonconductive sidewalls 116 a, 116 b. The sidewalls 116 a, 116b protect the layer 104 (e.g., tunneling barrier) from being shunted,for example, by any conductive material that may be re-deposited.

Referring to FIG. 1G, a second hard mask is deposited on the etchbarrier 116. For example, a second hard mask 118 is deposited on theetch barrier 116. Referring to FIG. 1H, a second photoresist isdeposited on the second hard mask and photolithography is used topattern the second photoresist. For example, a second photoresist 120 isdeposited on the second hard mask 118 and photolithography is used topattern the second photoresist 120 to expose portions of the second hardmask 118.

Referring to FIGS. 1I and 1J, an etching process is used to etch theexposed portions of the second hard mask, and the second photoresist isremoved. For example, an etching process (e.g., reactive ion etching) isused to etch the second hard mask 118 with the photoresist 120 acting asa mask, and after the etching of the second hard mask 118, thephotoresist 120 is stripped away

Referring to FIG. 1K, the exposed portions of the base and the etchinglayer are etched. For example, the exposed portions of the layers base100 and the etching layer 116 are etched using an ion beam etchingprocess to form a second intermediate structure 122. In particular,layers 102, 103 are etched. During the etching, the tunnel barrier 104remains protected by the vertical walls of 116 a, 116 b and second hardmask 118 from any re-deposition that might result from milling of layers102, 103 during ion beam etching.

Referring to FIG. 1L, an endcap is deposited on the second intermediatestructure. For example, an end cap 124 is disposed on the secondintermediate structure 122. In one example, the end cap is siliconnitride.

Referring to FIG. 2, an example of a process to pattern amagnetoresistance stack having two hard masks is a process 200. In oneexample, process 200 is performed under vacuum.

Process 200 deposits a multilayer magnetoresistance stack on a substrate(202) and deposits a first hard mask on the multilayer magnetoresistancestack (206), for example as depicted in FIG. 1A.

Process 200 deposits a first photoresist on the first hard mask (208)and patterns the first photoresist using photolithography to exposeportions of the first hard mask (212), for example, as depicted in FIG.1B.

Process 200 etches the exposed portions of the first hard mask (216),for example, as depicted in FIG. 1C. Process 200 strips the firstphotoresist (222), for example, as depicted in FIG. 1D.

Process 200 etches the exposed portions of the magnetoresistance stackand the first hard mask to form an intermediate structure (226), forexample, as depicted in FIG. 1E. Process 200 deposits an etch barrier onthe intermediate structure (232), for example, as depicted in FIG. 1F.

Process 200 deposits a second hard mask on the etch barrier (242), forexample, as depicted in FIG. 1G. Process 200 deposits a secondphotoresist (246) and patterns the second photoresist usingphotolithography to expose portions of the second mask (250), forexample, as depicted in FIG. 1H.

Process 200 etches the exposed portions of the second hard mask (254),for example, as depicted in FIG. 1I. Process 200 strips the secondphotoresist (258), for example, as depicted in FIG. 1J.

Process 200 etches a portion of the second hard mask, a portion of theetch barrier and a portion of the base to form a second intermediatestructure (264), for example, as depicted in FIG. 1K. Process 200deposits a capping layer on the second intermediate structure (268), forexample, as depicted in FIG. 1L.

The processes described herein are not limited to the specific examplesdescribed. For example, the process 200 is not limited to the specificprocessing order of FIG. 2 respectively. Rather, any of the processingblocks of FIG. 2 may be re-ordered, combined or removed, performed inparallel or in serial, as necessary, to achieve the results set forthabove. In another example, processing blocks 232 and 242 to form thesidewalls 116 a, 116 b may be repeated for each tunneling barrier 104 ina magnetoresistance stack.

Elements of different embodiments described herein may be combined toform other embodiments not specifically set forth above. Variouselements, which are described in the context of a single embodiment, mayalso be provided separately or in any suitable subcombination. Otherembodiments not specifically described herein are also within the scopeof the following claims.

What is claimed is:
 1. A method, comprising: depositing on a substrate amagnetoresistance stack comprising a plurality of layers comprising afirst set of one or more magnetoresistance layers and a second set ofone or more magnetoresistance layers; depositing a first hard mask onthe magnetoresistance stack; depositing a first photoresist on the firsthard mask; patterning the first photoresist using photolithography toexpose portions of the first hard mask; etching the exposed portions ofthe first hard mask to expose a portion of the magnetoresistance stack;stripping the first photoresist; etching the exposed portions of themagnetoresistance stack and the first hard mask to form a firstintermediate structure having a base and a pillar structure; depositingan etch barrier on the first intermediate structure; depositing a secondhard mask on the etch barrier; depositing a second photoresist on thesecond hard mask; patterning the second photoresist usingphotolithography to expose portions of the second hard mask; etching theexposed portions of the second hard mask; stripping the secondphotoresist; etching a portion of the second hard mask, a portion of theetch barrier and a portion of the base to form a second intermediatestructure; and depositing a capping barrier on the second intermediatestructure.
 2. The method of claim 1, wherein etching the exposedportions of the magnetoresistance stack and the first hard mask to formthe first intermediate structure having the base and the pillarstructure comprises etching the exposed portions of themagnetoresistance stack to form the first intermediate structure havingthe base, the base comprising: a conductive layer on the substrate; andan active element on the conductive layer.
 3. The method of claim 1,wherein etching the exposed portions of the magnetoresistance stack andthe first hard mask to form the first intermediate structure having thebase and the pillar structure comprises etching the exposed portions ofthe magnetoresistance stack and the first hard mask to form the firstintermediate structure having the pillar structure, the pillar structurecomprising: the first hard mask; capping material; an active element;and a tunneling barrier.
 4. The method of claim 1, wherein depositing onthe substrate the magnetoresistance stack comprises depositing one of atunneling magnetoresistance (TMR) stack or a magnetic tunnel junction(MTJ) stack.
 5. The method of claim 1, wherein depositing the cappingbarrier comprises depositing a capping barrier comprising siliconnitride.
 6. The method of claim 1, wherein depositing themagnetoresistance stack on the substrate comprises depositing amagnetoresistance stack comprising a layer of magnesium oxide.
 7. Themethod of claim 1, wherein depositing the magnetoresistance stack on thesubstrate comprises depositing a magnetoresistance stack comprising alayer of silicon nitride.
 8. The method of claim 1, wherein depositingthe magnetoresistance stack on the substrate comprises depositing themagnetoresistance stack on the substrate, the substrate comprising oneof silicon dioxide or silicon nitride.
 9. The method of claim 1, whereindepositing the first hard mask or the second hard mask comprisesdepositing silicon dioxide.
 10. The method of claim 1, whereindepositing an etch barrier comprises depositing an etch barriercomprising silicon nitride.
 11. The method of claim 1, wherein etchingthe exposed portions of the magnetoresistance stack comprises etchingusing an ion beam etching process.
 12. The method of claim 1, whereinetching the portion of the second hard mask, the portion of the etchbarrier and the portion of the base comprises etching using an ion beametching process.
 13. The method of claim 1, wherein depositing on thesubstrate a magnetoresistance stack having a plurality of layerscomprising the first set of one or more magnetoresistance layers and thesecond set of one or more magnetoresistance layers comprises depositingon the substrate a magnetoresistance stack having the plurality oflayers comprising: a first set of one or more magnetoresistance layerscomprising: one or more active elements; and a tunneling barrier layer;a second set of one or more magnetoresistance layers comprising anactive element. 14-20. (canceled)